A variety of diseases exist which require regular treatment by injection of a medicament. Such injection can be performed by either medical personnel or by patients themselves. As an example, type-1 and type-2 diabetes can be treated by patients themselves by injection of insulin doses once or several times per day. It is known to couple a supplemental device to an insulin injection device for recording information about the doses that are administered. Supplemental devices may be used to record information about the various times at which insulin doses are administered and the quantity of insulin administered during each such dose.
One previously proposed insulin injection device, specifically the Solostar™ injection pen sold by Sanofi, is provided with a window in its outer surface (hereafter referred to as a dosage window). A sleeve inside the Solostar™ injection pen (known as the number sleeve) is caused to rotate when an amount of insulin is dialled or dispensed. Numbers on the number sleeve successively align with the dosage window as the sleeve rotates. When an amount of insulin has been dialled, the number corresponding to the dialled amount of insulin (in International Units) is displayed in the dosage window. When insulin is dispensed, rotation of the number sleeve causes the number displayed in the dosage window to be that associated with the dialled amount of insulin remaining in the pen yet to be dispensed.
WO2011/117212 describes a supplemental device, provided with optical character recognition (OCR) functionality, for reading numbers aligned with the dosage window of an injection device to determine quantities of insulin dialled or delivered. Supplemental devices which use OCR for this purpose obstruct the view of numbers aligned with the dosage window in use. A display unit may therefore be provided for displaying an indication to a user of the determined amount of insulin dialled or, in the case of an injection, for displaying an indication of the progress of the injection.
It will be appreciated that indications on such a display unit are required to correspond with the actual quantity of insulin dialled or dispensed. In other words, the indications shown by the display unit should be updated as quickly as possible after a quantity of insulin has been dialled or dispensed. In the case of the Solostar™ injection pen for instance, an amount of insulin is selected by a user turning a dose dialling knob in a series of twists. After each such twist, the indication shown by the display unit of the currently selected insulin amount should be updated as quickly as possible to reduce the likelihood of a user unnecessarily dialling additional dose. Optimally, the optical character recognition algorithm used to determine the particular numbers aligned with the dosage window should be as efficient as possible.
Aspects of the present invention have been conceived with the foregoing in mind.